how to check a tachometer

• 2022-01-07

The speed is a barometer of the working state of the engine. When the engine is in idle and neutral gear, the speed shall be stable and within a reasonable range; When stepping on the accelerator pedal in neutral gear, the speed shall change smoothly with the smooth rise and fall of the pedal. When the accelerator pedal is stabilized, the tachometer pointer shall remain at a certain speed scale. If the idle speed of the engine is high or low, the speed is unstable, and the tachometer shakes, it indicates that there is a fault in the engine.

When the tachometer is abnormal, the common fault causes are as follows:

1. It may be that the speedometer of the vehicle's instrument assembly has failed, resulting in the pointer of this meter not rotating.

2. It may be that the wheel speed sensor of the vehicle has failed, resulting in the non rotation of this meter.

3. It may be that the mileage sensor of the vehicle has failed, resulting in the meter not rotating.

Fault of Tachometer diagnosis methods:

1.Thread removal method.

When the reading of automobile electrical instrument is abnormal, and it is analyzed and inferred that there may be grounding fault in the sensor or between the sensor and the indicating instrument, the wire removal method is often used for inspection.

2.Grounding method.

When the reading of automobile electrical instruments is abnormal, through analysis and inference, it may be that the sensor is poorly grounded or damaged, and there is an open circuit fault in the wire between the sensor and the indicating instrument, the grounding method is often used for inspection. The cause and location of the fault can be determined by grounding the relevant terminal through the wire.

3.Short circuit method.

When other electrical instruments work normally and only the instruments connected to the voltage regulator (such as fuel gauge, electromagnetic water temperature gauge, etc.) do not work, the short-circuit method can be used for inspection. Short circuit the input and output terminals of the regulator with wires. At this time, if the instrument pointer connected to the regulator deflects immediately, it is an internal fault of the regulator.

How to check a tachometer, the answers are below:
(1) Check whether the ignition coil terminal is in good contact.
(2) Check whether the black three hole socket behind the engine tachometer is in good contact.
(3) Check the working condition of the two hole socket with a multimeter. If the a socket is poorly grounded